Compacting metallic powders



G. o. MAISH ETAL 3,095,262

COMPACTING METALLIC POWDERS Filed Oct. 15, 1957 June 25, 1963 INVENTORS George 0. Maia/2 E/woad E \seaslw/fz ATTORNEY United States Patent 3,095,262 CGMPACTING METALLIC POWDERS George 0. Maish and Elwood F. Seasholtz, Bethlehem, Pa., assignors to Bethlehem Steel Company, a corporation of Eennsylvania Filed Oct. 15, 1957, Ser. No. 690,262 4 Claims. (Cl. iii-$9.3)

This invention concerns the compacting of metallic powders, particularly magnetic metallic powders such as iron, nickel and cobalt.

When fine dry metallic powder is passed vertically between rolls for the purpose of briquetting or compacting said powder, a considerable portion of the powder drains through the rolls as fines without being compacted, resulting in the formation of partially compressed, incompletely formed compacts, and necessitating the re-rolling of large amounts of the powder. Another problem encountered in the rolling of metallic powders is the dense dust atmosphere which exists in the rolling area and creates a continuing explosive hazard.

An object of this invention is to reduce the amount of powder which passes thru the rolls as fines during the rolling operation.

Another object is a method of rolling metallic powders which will produce strong, fully formed compacts.

Still another object is a reduction in the amount of dust present in the rolling area.

These objectives can be attained by magnetizing the metallic powder either prior to or simultaneously with the rolling operation.

The foregoing objects and the means whereby they are attained will be more fully understood from the following description and claims together with the drawings in which FIGURE 1 is a sectional view showing the overall hopper and roll arrangement.

FIGURE 2 is an elevation view showing the polarity of the wells for one form of this invention.

Referring to FIGURE 1, a magnetic coil 2 surrounds the inlet pipe 1 leading to hopper 3. Coil 2 thus magnetizes the fine metallic particles as they pass through its magnetic field on their way into hopper 3. Mixing a gas under pressure with the metallic particles to blow the particles through the inlet pipe 1 will eliminate the tendency of the metallic particles to clog the inlet pipe after they have been magnetized. The metallic particles flow vertically from the hopper 3 to smooth or pocketed rolls 4 which compress the particles into compacts or briquettes 5.

Referring to FIGURE 2, each roll has a central portion 6 that has a polarity opposite to the polarity of its end bearing portions '7. Furthermore, the polarity of a portion of each roll is opposite to the polarity of the corresponding portion in the mating roll.

One form of this invention consists of magnetizing the magnetic metallic powder by any convenient method before the powder is subjected to the rolling operation. The magnetized powder flocculates, and the free flowing characteristics of the powder are reduced, thereby enabling the powder to remain in the roll bite until it has been compacted, and lessening the amount of fines which leak thru the rolls without being compacted. This permits the use of maximum compressive forces in the rolls, which in turn causes strong, fully formed compacts to be produced.

3,995,262 Patented June 25., 1963 ice compacting the magnetic powder with magnetized rolls which are preferably magnetized in such a manner that "a magnetic flux passes between the opposing roll surfaces, thereby subjecting the magnetic powder being rolled to a magnetic field. This magnetizes the powder and holds it firmly in the roll bite until compression has taken place, reduces the number of fines passing thru the rolls without being compacted, and creates a relatively dust free atmosphere.

Any suitable means may be employed to magnetize the rolls. A desirable arrangement is to so magnetize the rolls that there are poles of like form at each roll end and an opposite pole in the central rolling area, with the central area of one roll being magnetized north, and the central area of the opposing roll being magnetized south. The rolls may be permanently magnetized, one magnetization being relied on, or suitable coils may be employed which are continuously supplied with current during the rol'lin g operation.

As an example of this invention, iron powder directly reduced from Swedish ores was passed thru pocketed rolls which had been permanently magnetized so that one roll was magnetized north in the central area and south at the roll ends, while the opposing roll was magnetized south in the central area and north at the roll ends. Fully formed briquettes were produced with less than 10% fines passing thru, whereas the same procedure followed earlier with non-magnetized rolls allowed 60% of the powder to pass thru as fines. In addition, the rolling area was relatively free of dust when magnetized rolls were used.

The term magnetic metallic powder as used herein denotes metallic powders which are capable of being magnetized.

We claim:

1. A method of compacting magnetic metallic powders which comprises magnetizing said powder and compacting the magnetized powder by passing said powder between a pair of magnetized compacting surfaces.

2. The method of claim 1, in which the compacting surfaces are a pair of rolls.

3. The method of claim 1, in which the compacting surfaces are magnetized in such a manner that a magnetic flux crosses between the compacting surfaces.

4. The method of claim 3, in which the compacting surfaces consist of a pair of rolls.

References Cited in the file of this patent UNITED STATES PATENTS 1,930,788 Buckner Oct. 17, 1933 1,981,468 Roseby Nov. 20, 1934 2,247,376 Heuer July 1, 1941 2,384,215 Toulmin Sept. 4, 1945 2,435,227 Lester Feb. 3, 1948 2,437,127 Richardson Mar. 2, 1948 2,771,637 Silvasy et a1 Nov. 27, 1956 2,849,312 Peterman Aug. 26, 1958 FOREIGN PATENTS 571,598 Great Britain Aug. 31, 1945 

1. A METHOD OF COMPACTING MAGNETIC METALLIC POWDERS WHICH COMPRISES MAGNETIZING SAID POWDER AND COMPACTING THE MAGNETIZED POWDER BY PASSING SAID POWDER BETWEEN A PAIR OF MAGNETIZED COMPACTING SURFACES. 